1. Field of the Invention
This invention relates to a water-soluble viscosity increasing agent and a liquid detergent composition containing the same and, more particularly, to a water-soluble viscosity increasing agent having excellent stability and solubility in a solution of various surface active agents and to a liquid detergent composition possessing a proper viscosity and homogeneousness containing said water-soluble viscosity increasing agent.
2. Description of the Background
Viscosity increasing agents are used in order to impart an appropriate viscosity to solutions of various surface active agents such as, for example, anionic, cationic and nonionic surface active agents, and have a wide variety of applications, e.g., for liquid detergents, cosmetics, paints, adhesives, dyestuff and the like. As viscosity increasing agents to be used with said solutions of a surface active agent, polyoxyethylene (hereinafter abbreviated to "POE") linear fatty acid ester type compounds, including POE linear fatty acid esters and POE methylglucoside linear fatty acid esters, and water-soluble polymers such as hydroxyethyl cellulose, methyl cellulose, polyvinyl pyrrolidone and the like are known in the art.
The viscosity increasing agents of the POE linear fatty acid ester type, however, tend to hydrolyze in an aqueous system and have a poor viscosity stability. On the other hand, the viscosity increasing agents of the water-soluble polymer type tend to salt out in a strong electrolyte solution containing a certain kind of an anionic surface active agent or inorganic salt, and thus have a poor solubility to such electrolyte. This imposes a serious limitation to the formulation, for example, of shampoos, when one intends to increase their viscosity.
There have been, therefore, strong demands for the development of a viscosity increasing agent possessing a good viscosity stability and an abundant solubility to solutions of various surface active agents, including anionic, cationic and nonionic surface active agents.